Thermophysical properties study of micro/nano materials

Thermal transport in micro/nano materials is very critical, not only because the thermal property may have important influence on the performance of the materials, but also because the change of this property can reflect the inner structure change. Due to the complicated structure and small scale, the thermal properties of biomaterials, such as silkworm silk, spider silk and human head hair, are still not fully understood. Experiments are conducted on silkworm silk, spider silk and human head hair to explore their thermal properties and potential applications. This work reports on the first time study of thermal transport in the axial direction of single silkworm silks. The measured thermal diffusivity of relaxed silkworm silk and thermal conductivity are 0.39 × 10-6∼2.03 × 10-6 m2 s-1 and 0.54∼6.53 W m-1 K-1, respectively. The thermal diffusivity of silkworm silk increases up to 263% upon elongation up to 63.8%. For one of the samples studied (sample 5), its thermal conductivity goes up to 13.1 W m-1 K-1 after elongation of 68.3%, surpassing many other polymers. Three factors combine together to give rise of the remarkable thermal diffusivity increase: alignment improvement of β–sheets blocks, straightening of α– and random coils under stretching, and structural transformation from α–helices and random coils to β–sheets crystal by elongation (confirmed by our Raman spectroscopy study). Thermal path break-down is observed when elongation is beyond 63.8%. Our Raman spectroscopy study confirms this speculation: after 60% elongation, the Raman frequency started to increase, indicating the internal stress has been released due to internal structure break-down. Through series of experiments, a linear relationship between the effective thermal diffusivity and pressure-which has an effect on the effective thermal diffusivity in the form of gas conduction-is discovered and proved. By testing samples with different length, the effect of radiation and gas conduction can be eliminated. In the second part, this work reports on the much more accurate characterization of thermal transport in the axial direction of single silkworm silk, spider silk and human head hair (three parts: at the root, in the middle, and at the tip). The measured real thermal diffusivity of silkworm silk, spider silk and human head hair is 3.68 × 10-7 m2 s-1, 3.53 × 10-7 m2 s-1, 1.53 × 10-7 m2 s-1 (at the root), 1.40 × 10-7 m2 s-1 (in the middle) and 1.49 × 10-7 m2 s-1 (at the tip), respectively. The thermal conductivity and effective emissivity of the materials can also be calculated with the given value of volume-based specific heat (ρcp). After characterizing the original samples, the study of thermal transport in the axial direction of single filaments of silk (Bombyx mori) fibroin before and after heat treatment is performed. The measured thermal diffusivity of the original silk fibroin fiber ranges from 4.05 × 10-7 to 4.65 × 10-7 m2 s-1. After heat treatment (from about 140 C to about 220 C) and subtracting the gold and radiation effect, the real thermal diffusivity of silk fibroin type 1, 2 and 3, increase by 38.12%, 20.72% and 21.35%, respectively. The sample diameter change is almost negligible which is proved by checking the diameter of the sample at the same place before and after heat treatment by SEM. Raman analysis was performed on the original and heat-treated (heated at about 147 C and 179 C) samples. After the heat treatment at 147 C, the peaks at 1081, 1230 and 1665 cm-1 become slightly sharper, which is a probable sign of structural transformation from amorphous region to crystalline region. According to the literature, a model composed of amorphous regions, crystalline regions and laterally ordered regions is proposed to explain the structural changes induced by heat treatment. Due to the close packing of the more adjacent laterally ordered regions, the number and size of the crystalline regions of Bombyx mori silk fibroin increased by heat treatment. Thus the thermal properties of the samples are significantly improved

Influences of Umbilical Cord Mesenchymal Stem Cells and Their Exosomes on Tumor Cell Phenotype

[EN] Backgrounds: Umbilical cord mesenchymal stem cells (UCMSCs) are derived from umbilical cord tissue. Due to their low immunogenicity, easy availability, mature culture technology, and lack of ethical controversy, they have gradually emerged as a focal point in stem cell research. Exosomes are cell-derived vesicles with a structure consistent with the cell membrane, primarily functioning as carriers to transport substrates for intercellular communication and regulation. Presently, both stem cells and their exosomes have emerged as highly promising biopharmaceuticals widely utilized in various clinical studies, including wound healing, spinal cord injury, post-operative rehabilitation, neurological disorders, and autoimmune diseases. However, the safety of these biologics remains uncertain, with some studies suggesting the potential tumorigenicity of stem cells and their exosomes. The objective of this study was to investigate the effects of UCMSCs and their exosomes on four types of tumor cells. Methods: In this study, first of all, UCMSCs and their exosomes were isolated and characterized. Subsequently, the study was performed in cell experiments. The effects of UCMSCs and their exosomes on four types of tumor cells (blast cancer cell line, gastric cancer cell line, glioma cell line, lung cancer cell line) were observed through co-culture experiments. The observables included the effects on in vitro phenotype and in vivo growth characteristics. Changes in gene expression were analyzed using high-throughput sequencing technology to elucidate the biological functions and roles of UCMSCs and their exosomes on tumor cells. Results: UCMSCs were successfully isolated, cultured, and identified. They demonstrated the capacity for differentiation into adipocytes, osteoblasts, chondrocytes, and neuron-like cells, indicating their multi-lineage differentiation potential. The UCMSCs-exos exhibited a diameter ranging from 30 to 150 nm, with an average size of 126.62 ± 1.64 nm, and showed increased expression of Tsg101, CD9, and CD63 proteins (P 0.05). However, in LN-229 cells, ROS and MDA levels were reduced, and SOD levels were increased in the UCMSCs group compared to the UCMSCs-exos group (P 0.05). In contrast, they inhibited the expression of NF-κB and p53 proteins in LN-229, with UCMSCs-exos demonstrating a more pronounced inhibitory effect (P < 0.05). Conclusions: In conclusion, this study successfully isolated UCMSCs and their exosomes. They promote the proliferation, migration, and invasion of four types of tumor cells involves altering the cell cycle. Additionally, UCMSCs and their extracellular vesicles are influenced by oxidative stress, and the NF-κB/P53 signaling pathway is implicated. These findings provide preliminary evidence that stem cells and their exosomes may not be suitable for patients with tumor diseases, offering an experimental basis for the potential clinical application safety of this technology in treatment. [ES] Antecedentes: Las células madre mesenquimales del cordón umbilical (UCMSCs) se derivan del tejido del cordón umbilical. Debido a su baja inmunogenicidad, fácil disponibilidad, tecnología de cultivo madura y falta de controversia ética, se han convertido gradualmente en un punto focal en la investigación con células madre. Los exosomas son vesículas derivadas de células con una estructura consistente con la membrana celular, que funcionan principalmente como portadores de sustratos de transporte para la comunicación y regulación intercelular. En la actualidad, tanto las células madre como sus exosomas se han convertido en productos biofarmacéuticos muy prometedores ampliamente utilizados en diversos estudios clínicos, como la cicatrización de heridas, las lesiones de la médula espinal, la rehabilitación postoperatoria, los trastornos neurológicos y las enfermedades autoinmunes. Sin embargo, la seguridad de estos productos biológicos sigue siendo incierta, y algunos estudios sugieren la posible tumorigénesis de las células madre y sus exosomas. El objetivo de este estudio fue investigar los efectos de las UCMSCs y sus exosomas en cuatro tipos de células tumorales. Métodos: En este estudio, en primer lugar, se aislaron y caracterizaron las UCMSC y sus exosomas. Posteriormente, el estudio se realizó en experimentos celulares. Los efectos de las UCMSC y sus exosomas en cuatro tipos de células tumorales (línea celular de cáncer de blasto, línea celular de cáncer gástrico, línea celular de glioma y línea celular de cáncer de pulmón) se observaron a través de experimentos de cocultivo. Los observables incluyeron los efectos sobre el fenotipo in vitro y las características de crecimiento in vivo. Los cambios en la expresión génica se analizaron utilizando tecnología de secuenciación de alto rendimiento para dilucidar las funciones biológicas y los roles de las UCMSC y sus exosomas en las células tumorales. Resultados: Las UCMSC fueron exitosamente aisladas, cultivadas e identificadas. Demostraron la capacidad de diferenciación en adipocitos, osteoblastos, condrocitos y células similares a neuronas, lo que indica su potencial de diferenciación multilinaje. Los UCMSCs-exos exhibieron un diámetro que varió de 30 a 150 nm, con un tamaño promedio de 126.62 ± 1.64 nm, y mostraron una mayor expresión de las proteínas Tsg101, CD9 y CD63 (P 0,05). Sin embargo, en las células LN-229, los niveles de ROS y MDA se redujeron, y los niveles de SOD aumentaron en el grupo de UCMSCs en comparación con el grupo de UCMSCs-exos (P < 0,05). Además, las UCMSCs y las UCMSCs-exos no afectaron la expresión de las proteínas NF- κB y p53 en las células MDA-MB-231, BGC-823 y A549 (P > 0,05). Por el contrario, inhibieron la expresión de las proteínas NF-κB y p53 en LN-229, y las UCMSCs-exos demostraron un efecto inhibidor más pronunciado (P < 0,05). Conclusiones: En conclusión, este estudio aisló con éxito las UCMSC y sus exosomas. Promueven la proliferación, migración e invasión de cuatro tipos de células tumorales que implican la alteración del ciclo celular. Además, las UCMSC y sus vesículas extracelulares están influenciadas por el estrés oxidativo, y la vía de señalización NF-κB/P53 está implicada. Estos hallazgos proporcionan evidencia preliminar de que las células madre y sus exosomas pueden no ser adecuados para pacientes con enfermedades tumorales, ofreciendo una base experimental para la posible seguridad de la aplicación clínica de esta tecnología en el tratamiento

Temporal Association Rule Mining in China’s Closed-end Fund Data

Financial market plays an important role in economy. Although funds developed only a few years in China, it has been a focal point in research and practice. The conventional methods analyzing fund data are fundamental analysis and technical analysis. Data mining can extract implicit, previously unknown and potentially useful knowledge from data. This paper presents the new technique to analyze China’s closed-end fund data and temporal association rules (TAR) are discovered which reflect the relationship among open price, close price, trading volume and grail index. Experimental results show some interesting outcomes

The crossing number of locally twisted cubes

The {\it crossing number} of a graph $G$ is the minimum number of pairwise intersections of edges in a drawing of $G$. Motivated by the recent work [Faria, L., Figueiredo, C.M.H. de, Sykora, O., Vrt'o, I.: An improved upper bound on the crossing number of the hypercube. J. Graph Theory {\bf 59}, 145--161 (2008)] which solves the upper bound conjecture on the crossing number of $n$-dimensional hypercube proposed by Erd\H{o}s and Guy, we give upper and lower bounds of the crossing number of locally twisted cube, which is one of variants of hypercube.Comment: 17 pages, 12 figure

Application Research and Practice of TBL Innovative Teaching Method in the Course of Clinical Biochemical Testing Technology

The purpose of this study is to explore the practical application effect of TBL innovative teaching method in the course of clinical biochemistry test technology. The research object is all undergraduate students in the laboratory major of 2018 medical school of our university. The research method is comparative experiment method, the teaching method of LBL teaching is set as control group, while the experimental group adopts TBL teaching method. By the final teaching evaluation and the data collected in the process, the influence of TBL teaching methods on the teaching effect of the course is compared and analyzed. The evaluation methods are combined with subjective and objective evaluation. The evaluation methods include questionnaire, student mutual evaluation, final test and other multiple ways. And the results of this study showed that the average score of the experimental group using TBL teaching method was significantly higher than that of the control group using traditional teaching method. In addition, through the process evaluation, it was found that the students in the experimental group were superior to the students in the control group in terms of learning interest, communication ability and learning methods. As a result, the application of TBL teaching method in the teaching of clinical biochemistry test obviously promotes the teaching quality and effect of this course